Fanoodi - Department of Mechanical Engineering, Islamic Azad University, Birjand Branch, Birjand, Iran
Moghiman - Department of Mechanical Engineering, Ferdowsi University, Mashhad, Iran

This paper describes the modifications and evolution of a thermal pulse combustion model for predicting the combustion oscillations of an aerovalved 250 kW pulse combustor incorporating a NOx formation-combustion model. Several variations of the model for inlet flow of reactants to the combustor have been proposed and investigated: steady inlet flow, sinusoidal inlet flow and modified sinusoidal inlet flow. The comparison of the predicted oscillations of three inlet configurations with experimental results indicates that the modified sinusoidal inlet flow (coupling the frequency of the periodic inlet flow of air with pressure oscillations within the combustor) gives the most realistic behavior. The model is used to investigate the influence of different boundary conditions on combustion scillations and NOx production in the pulse combustor. For example the results show that the exponential dependence of NOx emissions on equivalence ratio φ and NOx emissions were affected by frequency (i.e. tailpipe length). Also NOx values for steady conditions were much greater than oscillatory conditions as expected. The results identify the operating conditions for which continuous oscillations, steady flames and flame extinction occur.(For example at the highest wall temperature the oscillation dies out, but is replaced by a steady flame). These results show good agreement with experimental data.

Combustion Chamber; Pulse Combustor; NOx Formation